Influence of molecular structure on high-field phenomena in LDPE films

The authors have investigated the high-field phenomena in low-density polyethylene (LDPE). The objective of this paper is to study the relationship between molecular structure and the high-field phenomena at high temperature near the melting point of LDPE. The results can be summarized as follows. (1) The high-field current and the breakdown strength strongly depend upon film density determined by the concentration of methyl group. (2) The breakdown strength can be qualitatively estimated from the measurement of the high-field current. This incident as well as the above result suggests that a thermal process takes part in the dielectric breakdown of LDPE film at 90°C. (3) Both the type and the concentration of carbonyl groups affect the high-field current of LDPE